Construction of roofs of buildings and the like



April 22, 19411. A. H, PANDYA 2,239,399

CONSTRUCTION OF ROOFS 0F BUILDINGS AND THE LIKE Filed March 17, 195.9 5Sheets-Sheet l April 22, 1941. A. H. PANDYA 2,239,399

7 CONSTRUCTION OF RQOFS 0F BUILDINGS AND THE LIKE FiledMarch 17, 1939JSheets-Shet s Patented Apr. 22, 1941 CONSTRUCTION OF ROOFS OFBUILDINGS- AND THE LIKE Anant I-Iiralal Pandya, Westminster, London;

England Application March 17, 1939, Serial No. 262,346 In-Great-BritainMarch 23, 1938 5. Claims.

This invention relates to" roofs or other parts of structures or ofsubdivisions of structures required to carry loads distributed over alarge area without the aidof supporting members disposed within theboundaryof theroof or other part.

An object of this'ijnvention is to provide a ridged roof or other ridgedconstruction (-e. g. a hopper floor) adapted to cover extensivesubstantially rectangular spaces without any trusses or otherstructuralmembers projecting below the planes of the ridged structure. A furtherobject is to reduce-materially the maximum positive bending momentsinthe structural members and to provide a structure having a high strengthfactor per unit of weight. Another object is to provide simplified roofconstruction which enables satisfactory lighting and ventilation to beeasily attained and the cost of maintenance to be kept-low.

In accordance with this invention, a ridged roof or other ridged partcomprises a plurality of continuous beams which are disposedperpendicularly or substantially so to the ridge line and which aresupported by means of columns or equivalent supports at their ends only,said continuous beams being'cranked at the ridge line so as to lie inthe planes of the roof or other ridged part and receiving the roof orequivalent loading/and three boom members disposed respectively alongsaid ridge line and along eave or valley or other fold lines of the roofor other ridged part, said boom membersco-operating with said continuouscranked beams to form two inclined or vertical girders which providevirtual support for said beams at cranking points therein.

By the term continuous cranked beam is therefore meant. a beam in theform of a series ofstraightlengths lying in a common plane and meetingone another at a sharp elbow at the cranked portion orportions, eachcranked" portion beingrigid enough to transmit substantial bendingmoment from one to the other of the adjoining straightportions of thecranked beam; The several straight portions, of each continuous crankedbeam thus. form vertical" members of the said girders.

Thisinvention is especially applicable to,mu1 tiple-pitch structures,and according-to the invention in another aspect a roof or other part ofthe multiple-pitch type comprises a plurality of continuous beams whichare disposed perpendicularly, or substantially so to the ridge lines,said continuous beams being cranked atthree or more points so as to liein the planes of the roof crating with the portions of said continuouscranked beams between said two ridge lines to form a plurality ofinclined or vertical girders which are supported at their ends onlyandwhich provide virtual support for said beams at cranking pointstherein. The continuous cranked beams in this case are convenientlyprovidedwith supporting columns at their ends, or in placerof some orall of the columns there may be employed equivalent relatively rigidsupports such as walls or stiii girders.

The invention will be further described with reference to variousexamples of roof construction shown in the accompanying drawings, inwhich: i i

Fig. I is a diagram of a single-pitch roof with a central ridge,

Fig, 2 shows a multiple-pitch roof with a middle valley and two ridges,

Fig. 3 shows a multiple-pitch roof with tw valleys and'three ridges, I V

Fig. 4 shows a north-light or saw-tooth type of roof with multiplegables,

Fig. 5 shows a single-pitch roof with the middle portion raised toaccommodate sky or lantern lights, or ventilators,

Fig. 6 shows a double-pitch roof with the middle portion of each gableraised, and

Figs. 7 and 8 are sections of constructional de- In the constructionshown'in Fig. 1 there are shown by way of example five continuouscranked beams each consisting of two straightportions 2a and 2b unitedby an elbow portion 4 or 4". These cranked beams are supported only attheir ends on columns I uniformly distributed along the longitudinalsides of the structures. A ridge member 3 crosses the cranked beams atright angles, the points of intersection being coinci- '-dent with thecranking points 4 and 4 of the cranked beams. The cranked beams arefurther tom booms of a second girder, which lies in the other roof planeand of which the straight portions 2b of the cranked beams formverticals. The two end cranked beams are each provided with a gable tie6 which takes up the horizontal components of the girder reactions.

The roof loads due to any causes and applied in any direction aretransferred to the straight portions of the cranked beams by anysuitable secondary system (not shown) such as purlins or roof slabs,which rest directly on the cranked beams. These roof loads thus causethe cranked beams to bend. However, since at the cranking points 4 thecranked beams receive virtual support from the relatively stiff girdersof which they form the verticals, and furthermore since the crankedbeams are continuous over the cranking points 4 which receive thisvirtual support (that is, since negative bending moments can betransmitted from one straight portion 2a through the cranking portion 4or 4 to the adjoining straight portion 2b), the maximum positive bendingmoments in the cranked beams are substantially lower than they would bein corresponding discontinuous beams of the same span as the straightportions of the cranked beams.

It will be evident that the cranked beams are subjected both to bendingin directions transversely to the planes of the roof under the influenceof the roof loads incident on them, and also to axial strain or bendingin the planes of the roof due to their acting as elements of thelongitudinally disposed roof girders.

These girders areshown as trus es without diagonal bracing in their ownplanes, such bracing may be introduced if desired, or the girders may beof the Vierendeel type, which is especially advantageous inreinforced-concrete construc tion. (In the Vierendeel truss theverticals are rigidly fixed to the booms and are designed to take up thebending moments imposed on them by the shear load in the truss, so thatdiagonal bracing is dispensed with.)

As a further alternative, which is particularly suitable forreinforced-concrete construction, the girders, instead of being trusses,may have continuous webs of slab form.

It is not essential for the end cranked beams to be continuous. Forexample these beams may be discontinuous at the ridge points 4', thesepoints in this case each being supported by an additional column I. Theconstruction shown in Fig. 1, when so modified, would have only threecontinuous cranked beams arranged in accordance with this invention.

The girders lie wholly in the planes of the roof and are supportedwithout the agency of tie rods, bracings or columns extending below theroof planes within the area covered by the roof.

Figs. 2 and 3 show how the construction described with reference to Fig.1 may be developed for roofs of wider span, without introducing anyinternal-columns or equivalent supporting members. In Fig. 2 each of thecranked beams is continuous from the eave member 5a to the eave member5b and consists of four straight portions 2a, 2b, 2c and 2d united byrigid cranking portions 611, 8 and 4b. The cranking portions 4a and 4bcoincide with the ridge members 3a and 31) respectively, and thecranking portion 8 coincides with a valley member 1 which forms thecommon bottom boom of two longitudinal girders having respectively topbooms 3a and 3b and verticals 2b and 2c. The only additional columnsrequired, as compared with Fig. 1, are the two columns H placed one ateach end of the valley member 7.

Provided the span of the roof girders is kept constant, the continuouscranked beams can be lengthened indefinitely by the introduction ofadditional cranking points along their total length and additional ridgeand valley boom members, with the additional columns for the last. Fig.3 shows by way of example a roof having three ridges.

In Fig. 4 a similar arrangement of continuous cranked beams is used fora north-light or sawtoothed type of construction in which the northerlyand southerly facing roof planes lie at different angles to thehorizontal and consequently the depth of the corresponding girders aredifferent. The action of the continuous cranked beams is, however,similar to that described with reference to Figs. 1 to 3, it beingimmaterial that successive straight portions of the cranked beams arealternately long and short.

Fig. 5 is an example of the application of the continuous cranked beamconstruction to a roof in which the points of cranking and thedeviations of the beams at these points are arranged to suit particularpractical requirements such as lighting, ventilation, head room and soforth. Each continuous beam is cranked at five points, coinciding withthe intersection points with the beams of five longitudinal boom membersl2a, 13a, 3, 13b, and'l2b. The end reactions of the girdersincorporating these boom members are taken by ties 6a, 6b and 6c and theend columns I. Fig. 6 shows a development of the design of Fig. 5 to adouble-pitch roof. In both these designs internal columns and internalties or bracings projecting below the roof planes are unnecessary.

The improved structure may be carried out in any desired structuralmaterial such as structural steel or reinforced concrete.

Fig. 7 shows by way of example one form of ridge cranking point, such as4 in Fig. 1, in welded structural steel construction. The continuouscranked beam comprises two straight portions 2a and 2b having theirridge ends cut off obliquely. The oblique ends are fillet welded toopposite sides of a fiat junction plate 20. The ridge boom member iscomposed of the uppermost two purlins Zia and 2| b welded to the topflange of the cranked beam and an angle bar 22 welded to the bottomflange of the cranked beam and to the plate 20.

Fig. 8 shows an alternative example of cranking point, such as a valleypoint 8 in Fig. 2. The lower ends of the two straight portions 2b and 2cof the cranked beam are cut off square, and their webs are butt weldedto a filling plate 24. The ends of the upper flanges of the portions 2band 2c, which are suitably bevelled, are butt welded together, and thelower flanges are butt welded to a bent filling strap 25 which is filletwelded to the plate 24. The valley boom member comprises the twochannels 26 fillet welded to the continuous web of the cranked beam atthe cranking point.

Although the invention has been described by way of example as appliedto roofs, it is to be understood that it is applicable to otherstructural elements required to carry loads distributed over a largearea without intermediate supporting members, such for example as floorsof hoppers and bins.

I claim:

1. A ridged structure comprising a plurality of parallel, continuouscranked beams located substantially in vertical planes and being rigidacross their cranking points, booms disposed at right angles to saidvertical planes along and rigidly secured to the aligned ends andcranking points, respectively, of said beams, a tie for each of the twooutermost cranked beams, each tie connecting the two ends of one of saidoutermost beams, and supports at the ends of all said cranked beams.

2. A ridged structure covering a substantially rectangular area andcomprising a plurality of girders occupying the respective roof planes,said girders including booms disposed along the folds and side edges ofthe structure and beams disposed transversely of and rigidly secured tosaid booms and extending from side edge to side edge of said area, saidbeams being cranked so as to lie in the several roof planes and rigidacross their cranking points, means disposed at the ends of said beamsalong the edge of said area for supporting said structure and horizontalties connecting the corresponding lower edges of pairs of girders at theends of the latter, said beams being capable of developing substantialnegative bending moments across said cranking points under the influenceof the virtual support afforded at such points by said girders, so thatsaid beams serve as continuous rafters, while their several straightportions act as stressed web bracing elements of said girders.

3. A ridged structure for carrying loads distributed over a large planearea, said structure being of the multiple-pitch type and comprising aplurality of girders which occupy respectively the several roof planes,supports for said girders disposed on the boundary of said plane area,and horizontal ties between the ends of each two of said girdersadjoining each ridge line for taking up the horizontal components of thegirder end I reactions, said girders comprising boom members disposedrespectively along the ridge lines and the other fold and side boundarylines of the ridged part, and beam elements which serve both as webmembers of said girders and as means for receiving the working loads,said beam elements' said girders to said continuous cranked beams atsaid points.

4. A multiple-pitch ridged structure for carrying loads distributed overa large area and comprising a plurality of beams disposed transverselyof the ridge lines and spanning in a continuous length from edge to edgeof said area, said beams being cranked in vertical planes respectivelyat a plurality of points so as to lie in the several planes of saidstructure, said cranked beams being rigid across their cranking points,booms disposed respectively along said ridge lines, other fold lines andside boundary lines of said structure at right angles to the verticalplanes of the cranked beams, said booms being rigidly secured to thealigned ends and cranking points respectively of said cranked beams andcooperating with said beams to form girders lying parallel to said ridgeline and in each of said several planes, respectively, means disposed onthe boundary of said structure for supporting the same, and means forresisting the horizontal components of the end reactions of saidgirders, said beams having continuity of effective section modulus oversaid cranking points so that they are able to develop at said points,under the influence of superficial loading and the virtual supportafforded to them at said points by said girders, negative bendingmoments of the same order of magnitude as the maximum positive bendingmoments developed in them intermediate said cranking points by suchloading.

5. A ridged structure of the multiple-pitch type which is required tocarry loads distributed over a large area, said structure comprising aplurality of girders disposed parallel to the ridge lines and eachoccupying a plane of the roof, so that said girders lie longitudinallyside by side, each being inclined to the adjacent girders and each pairof adjacent girders having one common boom, means disposed along theboundary of said area for supporting said structure, and means fortaking up the horizontal components of the end reactions of saidgirders, said girders comprising beams to receive said loads, said beamsbeing continuous over and cranked at said common booms and being rigidlysecured to said booms to serve both as web bracing elements of saidgirders and as continuous rafters which, under the influence of the roofloads and the virtual support afforded to them by said girders, developmaximum positive and negative bending moments of similar orders ofmagnitude, the former between and the latter at said cranking points.

ANANT HIRALAL PANDYA.

